Characterization of Boiler Blowdown Water from Steam-Assisted Gravity Drainage and Silica-Organic Coprecipitation during Acidification and Ultrafiltration

In thermally enhanced oil recovery operations, particularly in steam-assisted gravity drainage (SAGD), boiler blowdown (BBD) containing high concentrations of dissolved organic matter (DOM), dissolved silica, and total dissolved solids (TDS) is generated. To develop efficient tools for managing this blowdown, a detailed understanding of its chemistry is required. In this study, BBD was evaporated to yield similar to 66% condensate and similar to 33% concentrate blowdown (CBD). Detailed characterization of the BBD and CBD water was conducted. The effect of acidification was also studied. The acidification coprecipitates the silica and DOM, with over 90% of the silica and over 40% of the DOM precipitating at pH 4. Ultrafiltration treatment was also examined, and a major fraction of the silica and DOM in the CBD was found to foul a 100 kDa ultrafiltration membrane in the pH range of 7.5 to 9. The analysis revealed that the dominant fouling mechanism was cake filtration, indicating the formation of a silica-DOM precipitate layer on the membrane surface. These studies can provide insight regarding management options for SAGD disposal water.